How Can Sorting Keys Efficiently Sort Lists Based on Multiple Attributes?

Utilizing Sorting Keys for Multi-Attribute Sorting of Lists

Sorting a list of lists based on individual attributes is often straightforward. However, when multiple attributes are involved, a dilemma arises. Can we sort efficiently without multiple rounds of sorting?

To address this challenge, we introduce the concept of sorting keys. A sorting key acts as a function that assigns a unique value to each element in the list, determining the sorting order.

For instance, in the given list:

[[12, 'tall', 'blue', 1],
[2, 'short', 'red', 9],
[4, 'tall', 'blue', 13]]

To sort by both "tall/short" and "color," we can define a key function that returns a tuple based on these attributes:

key = lambda x: (x[1], x[2])

Using this key, we can sort the list using the sorted function:

s = sorted(s, key = key)

Alternatively, we can leverage the itemgetter function for faster performance:

import operator
s = sorted(s, key = operator.itemgetter(1, 2))

Furthermore, we can directly sort the list using the sort function with the specified key:

s.sort(key = operator.itemgetter(1, 2))

With sorted keys, we achieve efficient multi-attribute sorting without the need for multiple sorting passes.

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